Regarding a technique for transmitting/receiving a millimeter wave signal, Patent Literature 1 discloses a dielectric waveguide line. This dielectric waveguide line includes a pair of main conductor layers, two lines of via hole groups, and sub-conductor layers, wherein the main conductor layers are formed in parallel with a dielectric interposed between them. The via hole groups are formed at an interval equal to or shorter than a cutoff wavelength in the direction of signal transmission to electrically connect the main conductor layers. The sub-conductor layer is connected to the via hole groups and formed in parallel with the main conductor layers.
When an electric signal is transmitted by a waveguide region enclosed by the main conductor layers, the via hole groups, and the sub-conductor layers in the dielectric waveguide line, at least one of the main conductor layers is formed with slot holes for electromagnetically coupling with a high frequency transmission line. The high frequency transmission line is constituted by a microstrip line, and is formed at a position opposite to the slot holes. When the dielectric waveguide line is made as described above, it is easy to electromagnetically couple with another high frequency transmission line, and a signal can be transmitted. In addition, a waveguide line having stable characteristics from a microwave to a millimeter wave can be provided.
Regarding a technique for transmitting/receiving a millimeter wave signal, Patent Literature 2 discloses a wireless-type millimeter wave communication system. The millimeter wave communication system includes millimeter wave transmission means, millimeter wave reception means, and reflection means, wherein the millimeter wave transmission means includes a transmission antenna having a predetermined directivity and light emission means. The millimeter wave transmission means transmits a signal in a millimeter wave band. The millimeter wave reception means receives the millimeter wave signal from the millimeter wave transmission means. The reflection means is arranged to reflect the signal wave radiated from the millimeter wave transmission means and reflect a light, so that the reflected signal wave is incident to the millimeter wave reception means. With the above conditions, the millimeter wave transmission means is arranged with the light emission means almost in parallel with an output axis of the transmission antenna, so that the light emission means emits a light ray in the same direction as the signal wave.
In order to adjust an initial position of the reflection means, the angle of the transmission antenna is adjusted by means of visual check so that the light ray emitted in parallel with the output axis of the transmission antenna is incident upon the reflection means. Accordingly, the angle of the reflection means can be adjusted so that the light ray reflected by the reflection means is incident upon the reception antenna. When the millimeter wave communication system is configured as described above, the initial direction of the reflection means can be adjusted easily by only one person.